Re: return value optimization
On Dec 4, 8:28 am, terminator <farid.mehr...@gmail.com> wrote:
On Dec 4, 5:05 pm, aaragon <alejandro.ara...@gmail.com> wrote:
On Dec 4, 2:05 am, Kira Yamato <kira...@earthlink.net> wrote:
On 2007-12-04 00:26:52 -0500, aaragon <alejandro.ara...@gmail.com> sai=
d:
Hi,
I'm designing a Matrix class so I read what Bjarne Stroustrup has on=
section 22.4.6 about it. It shows that it is possible to eliminate t=
he
temporaries by delaying the construction of the object. In his examp=
le
(page 675):
struct MVmul {
const Matrix& m;
const Vector& m;
MVmul(const Matrix& mm, const Vector& vv) : (mm), v(vv) { }
operator Vector(); // evaluate and return result
};
inline MVmul operator*(const Matrix& mm, const Vector& vv)
{
return MVmul(mm,vv);
}
Now, I think that's cool, however, I have a question about the
converting function operator Vector(). The implementation could be
done there OR it can be done as a constructor of the Vector class,
right? Something like this:
class Vector {
// member variables
...
public:
// constructors
...
Vector(const MVmul& mvmul) {
// evaluate
}
...
// rest of the class
};
Now the question is, is an approach better than the other? I think
that both are equivalent, but I wanted to make sure asking to the
experts...
Definitely in the MVmul class.
--
-kira
Why?
It(MVmul) has to convert its second argument to a Vector in either
case.
regards,
FM.
No, that second argument is untouchable. Is passed as a constant
reference. A new vector is created within the operator Vector()
implementation. So I believe both approaches are equivalent.
a=B2
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